fix(wireguard): continue on ipv6 route add permission denial

internal/wireguard/run.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"strings"
 
 	"github.com/qdm12/gluetun/internal/netlink"
 	"golang.zx2c4.com/wireguard/conn"
@@ -108,10 +109,17 @@ func (w *Wireguard) Run(ctx context.Context, waitError chan<- error, ready chan<
 		// requires net.ipv6.conf.all.disable_ipv6=0
 		err = w.addRoute(link, allIPv6(), w.settings.FirewallMark)
 		if err != nil {
+			if strings.Contains(err.Error(), "permission denied") {
+				w.logger.Errorf("cannot add route for IPv6 due to a permission denial. "+
+					"Ignoring and continuing execution; "+
+					"Please report to https://github.com/qdm12/gluetun/issues/998 if you find a fix. "+
+					"Full error string: %s", err)
+			} else {
 				waitError <- fmt.Errorf("%w: %s", ErrRouteAdd, err)
 				return
 			}
 		}
+	}
 
 	ruleCleanup, err := w.addRule(
 		w.settings.RulePriority, w.settings.FirewallMark)